Hitherto, a number of transition metal complexes have been used as catalysts for organic synthesis reactions. In particular, since noble metal complexes are stable and easy in handling though they are expensive, there have been reported a number of synthesis researches using them as catalysts. In particular, there have been a number of reports on asymmetric catalysts used in asymmetric syntheses, i.e., asymmetric isomerization reaction or asymmetric hydrogenation reaction. Among them, especially metal complexes formed between metallic rhodium and an optically active tertiary phosphine are well known as catalysts for the asymmetric hydrogenation reaction. Such complexes typically include a rhodium-phosphine catalyst using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as "BINAP") as a ligand as disclosed in JP-A-55-61937. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".).
On the other hand, known ruthenium complexes, though there are not so many reports as compared with rhodium complexes, include those having BINAP or 2,2'-bis(di-p-tolylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as "T-BINAP") as a ligand, e.g., Ru.sub.2 Cl.sub.4 (BINAP).sub.2 (NEt.sub.3) (wherein Et represents an ethyl group, hereinafter the same) and Ru.sub.2 Cl.sub.4 (T-BINAP).sub.2 (NEt.sub.3), as reported in Ikariya et al., J. Chem. Soc., Chem. Commun., pp. 922 (1985). Further, asymmetric hydrogenation reactions of allyl alcohol and of isoquinoline-type alkaloid using Ru(CH.sub.3 CO.sub.2)(BINAP) as a ruthenium complex are reported in Noyori et al., J. Am. Chem. Soc., 109, pp. 1596 (1987) and ibid., 108, pp. 7117 (1986), respectively. Moreover, [Ru(BINAP)]X.sub.2 (wherein X represents ClO.sub.4, BF.sub.6, or PF.sub.6) is reported in H. Takaya et al., J. Org. Chem., 52, pp. 3174-3176 (1987) However, the state-of-the-art ruthenium complexes are not satisfactory in catalytic activity as well as durability.
Although metallic rhodium is a metal for excellent complex catalysts, it is limited in terms of place and quantity of production and is expensive. When used as a catalyst, it forms a large proportion in cost of the product, ultimately resulting in increase in cost of the final commercial products. While metallic ruthenium is cheaper than rhodium and appears promising as a catalyst for industrial application, it still has problems in its activity to cope with precision reactions and its range of application. Therefore, it has been keenly demanded to develop a catalyst which is inexpensive, has high activity and durability, and catalyzes asymmetric reactions to attain high optical yields, i.e., to produce reaction products having high optical purity.
As a result of extensive investigations with the purpose of meeting the above-described industrial demand, the inventors have discovered a novel ruthenium complex having high catalytic activity, which is usable either for general syntheses when the ligand thereof is optically inactive or for asymmetric syntheses when the ligand thereof is optically active. The present invention has been completed based on this finding.